1. Field of the Invention
The present invention relates to a car-stereo equipment having an operating-part main unit which is detachably provided, for example, with respect to an apparatus main unit.
2. Description of Background Information
As a measure for providing anti-theft capabilities with the trend of high-grade audio apparatuses, e.g., car stereo receiver/cassette-player, there already have been marketed car stereo equipments of the detachable type constructed in such a manner that the operating-part main unit, also called a control panel, is detachable, or of the quick release type constructed in such a manner that the principal electronics or apparatus main unit itself can be easily mounted into or detached from an installation position in a vehicle. As used herein, the term "operating-part main unit" is intended to mean a user actuated control unit or panel that is removably connected to an apparatus main unit. As used herein, the term "apparatus main unit" is intended to mean a unit having the principal electronics of the car-stereo equipment, such as the radio electronics, CD-player and tape player.
The detachable type car stereo equipments are designed to make it difficult to recognize the existence of the apparatus by removing the operating-part main unit from the apparatus main unit when the driver leaves the vehicle. On the other hand, the driver may often forget to remove the operating-part main unit from the apparatus main unit, so the driver is informed of such an overlook by an alarm in the case of some apparatuses.
FIGS. 1 and 2 show an example of a car-stereo receiver/cassette player of the detachable type which is designed to have the anti-theft feature mentioned above. An operating-part main unit 20 is detachably provided with respect to an apparatus main unit 10 which is mounted into a dash board or the like of a vehicle. A concave fitting portion 11 to receive the operating-part main unit 20 is formed at the front end of the apparatus main unit 10. A connector 12 is provided at a position near the right-hand side in the concave fitting portion 11.
A shutter 13 is slidably provided near the connector 12. By sliding the shutter 13 in the closing direction, each terminal in the connector 12, which will be explained hereinafter, will be concealed.
A cassette insertion slot 14 is formed at a central position in the concave fitting portion 11. An installation detection switch 15 for detecting the mounting of the operating-part main unit 20 is provided at a left-side position adjacent to the cassette insertion slot 14.
The connector 12 has a 5 V power supply terminal 12a, a data input/output (I/O) terminal 12b, an 8 V power supply terminal 12c, and a ground terminal 12d. A 5 V power supply circuit 17 is connected to the 5 V power supply terminal 12a. An 8 V power supply circuit 18 is connected to the 8 V power supply terminal 12c.
An electric power from a battery 31 of the vehicle is supplied to the 5 V power supply circuit 17 and 8 V power supply circuit 18 through a backup line 31a and an ACC line 31b. Reference numeral 30 denotes an ignition key. When the ignition key 30 is OFF, the power supply through the ACC line 31b is stopped. In this description, ON/OFF state of the ignition key 30 means the ON/OFF state of the ACC position.
A microcomputer 19 is connected to the I/O terminal 12b. The microcomputer 19 monitors the change in voltage at the ACC position in the ignition key 30 through a line 31d so that it recognizes that the ACC position is OFF when the voltage at the ACC position is at a low level.
A connector 21 which is to be connected to the connector 12 on the apparatus main unit 10 is provided on the rear side of the operating-part main unit 20. Various kinds of function buttons 22 such as preset buttons and the like are arranged at the bottom level on the front face of the operating-part main unit 20. A display section 23 to display information such as time, receiving frequency, and the like is provided at the middle level on the front face of the operating-part main unit 20. A cassette insertion port 24, which connects to the cassette insertion slot 14 on the apparatus main unit 10 when the operating-part main unit 20 is attached, is formed at the upper stage on the front side of the operating-part main unit 20.
The connector 21 has a 5 V power supply terminal 21a, a data I/O terminal 21b, an 8 V power supply terminal 21c, and a ground terminal 21d in correspondence to the terminals of the connector 12.
A microcomputer 25 is connected to the 5 V power supply terminal 21a and also to data I/O terminal 21b. The microcomputer 25 generates control signals to instruct the display of information such as time, receiving frequency, and the like in accordance with an operating mode of various kinds of function buttons 22. A display driver 26 controls the display operation of the display section 23 on the basis of the control signal from the microcomputer 25. An illuminating lamp 27 is connected to the 8 V power supply terminal 21c.
The fundamental operation of the car stereo equipment having a construction as mentioned above will now be described hereinafter.
An attached/detached state of the operating-part main unit 20 for the apparatus main unit 10 is discriminated by detecting the ON/OFF state of the installation detection switch 15 by the microcomputer 19. When the microcomputer 19 recognizes the attached state of the operating-part main unit 20, predetermined control data is sent to the data I/O terminal 12b.
In this instance, a driving electric power of 5 V is supplied to the microcomputer 25 in the operating-part main unit 20 through the 5 V power supply terminals 21a and 12a due to the coupling of the connectors 12 and 21. When receiving the driving electric power, the microcomputer 25 immediately executes a resetting operation and, after that, receives the control data from the microcomputer 19 through the data I/O terminals 12b and 21b, thereby allowing the display driver 26 to execute a predetermined operation on the basis of the control data received.
In this instance, the driving power of 8 V is supplied to the 8 V power supply terminal 12c. For instance, when a lamp light-on switch (not shown) of the vehicle is ON, the illuminating lamp 27 receives the driving power of 8 V and is lit on.
When the operating-part main unit 20 is removed from the apparatus main unit 10, the installation detection switch 15 is turned off. When the microcomputer 19 detects the OFF state of the switch 15, the transmission of the control data to the data I/O terminal 12b is stopped. Since the control data is not sent to the microcomputer 25 as mentioned above, even when the data I/O terminal 12b of the connector 12 may erroneously come into contact with the data I/O terminal 21b of the connector 21 after the operating-part main unit 20 has been removed, an erroneous display by the display section 23 or the like is prevented.
By sliding the shutter 13 in the closing direction after the operating-part main unit 20 has been removed from the apparatus main unit 10, each terminal in the connector 12 can be covered, so that an electric shock, short-circuit, or the like is also prevented.
The manner of an electric power supply from the battery 31 in association with the ON/OFF state of the ignition key 30 is as follows.
The electric power from the battery 31 is supplied to the 5 V power supply circuit 17 through the backup line 31a irrespective of the ON/OFF of the ignition key 30. The 5 V power supply circuit 17 supplies a driving electric power mainly to the microcomputer 19. When the driving of a CPU (not shown) in the microcomputer 19 is stopped, the 5 V power supply circuit 17 is used mainly as a backup power source of a memory (not shown) in the microcomputer 19.
When the ignition key 30 is turned on, the ACC line 31b and the battery 31 are connected and the electric power from the battery 31 is supplied to the 8 V power supply circuit 18 through the ACC line 31b. The 8 V power supply circuit 18 is mainly used as a driving power source of a tape loading mechanism (not shown), the illuminating lamp 27 on the operating-part main unit 20, and the like.
When the ignition key 30 is turned off, the ACC line 31b is disconnected from the battery 31. Regarding the 5 V power supply circuit 17, however, as mentioned above, even when the ignition key 30 is turned off, the electric power from the battery 31 is supplied to the 5 V power supply circuit 17 through the backup line 31a.
A consuming state of the electric power in the microcomputer 19 in association with the ON/OFF of the ignition key 30 is as follows.
The microcomputer 19 monitors the change in voltage at the ACC position in the ignition key 30 through the line 31d. When the microcomputer 19 detects a voltage drop at the ACC position as result of the turn-off of the ignition key 30, predetermined operations of the CPU in the microcomputer 19 are halted. In this state, only the memory in the microcomputer 19 receives the electric power from the 5 V power supply circuit 17, so that it continuously holds the information.
With respect to modes of the electric power consumption in the microcomputer 19, therefore, when the ignition key 30 is turned on, an ordinary operation processing mode or ordinary power consuming mode is set. However, when the ignition key 30 is turned off, predetermined operations of the CPU are halted, so that a low consuming mode is set and no dark current is generated from the 5 V power supply circuit 17, so that the inconvenience such that the voltage in the battery 31 is completely extinguished is eliminated. As used herein, the terms "low power consuming" and "low consumption" are intended to mean a rate of consumption less than the ordinary power consumption mode.
With the car stereo equipments installed in the vehicle having the ACC position as mentioned above, the microcomputer 19 monitors a change in voltage at the ACC position in the ignition key 30. When the ignition key 30 is turned off, predetermined operations of the CPU in the microcomputer 19 are halted and the low consuming mode is set. The generation of the dark current is, accordingly, eliminated and the complete extinction of the voltage of the battery 31 is prevented.
There are, however, vehicles of which the ignition key 30 does not have the ACC position described above. In case of the vehicles with an ignition key having no ACC position, the following inconvenience occurs.
With such vehicles, the backup line 31a and the ACC line 31b are connected via a short-circuit line 31c in the configuration shown in FIG. 2. Therefore, even when the ignition key 30 is turned off, the electric power from the battery 31 is continuously supplied to the 5 V power supply circuit 17 and 8 V power supply circuit 18, so that operations in such a state become equivalent to those in a state in which the foregoing ACC position is always turned ON.
Therefore, the CPU in the microcomputer 19 is placed in the operating mode irrespective of the turn-off of the ignition key 30, and the electric power for driving the CPU itself is also supplied in addition to the electric power to be supplied to only the memory in the microcomputer 19. Consequently, there arises a drawback such that a large amount of dark current flows and the energy of the battery may be consumed completely.
There are also types of audio apparatus that have a detachable operating-part main unit with an alarm. These apparatus are designed to sound the alarm when a user negligently fails or forgets to remove the operating-part. This alarm notification ensures that the user detaches the operating-part main unit from the apparatus main unit.
FIG. 3 shows a car-stereo equipment of the detachable type as an example of such audio apparatuses. In addition to the component elements of the car stereo shown in FIG. 2, a driving circuit 16a connected to the microcomputer 19 and a speaker 16 which is actuated by the driving circuit 16a are provided.
With such a construction as mentioned above, when the microcomputer 19 detects the negligence of the removal of the operating-part main unit 20 in the OFF state of the ignition key 30, the speaker 16 is activated through the driving circuit 16a, thereby generating an alarm sound.
That is, the microcomputer 19 detects the ON/OFF state of the ignition key 30. In the OFF state of the ignition key 30, when the microcomputer 19 detects by the installation detection switch 15 that the operating part main unit 20 is in an attaching state, the speaker 16 is activated through the driving circuit 16a so that alarm sound is generated, thereby warning the user that he has forgotten to remove the operating-part main unit 20.
When the ignition key 30 is turned off and the driver leaves from the vehicle, accordingly, the negligence of the removal of the operating-part main unit 20 is informed by the alarm sound, thereby the driver can be aware that he has forgotten to remove the operating-part main unit 20 from the apparatus main unit 10.
With the conventional car-stereo equipments described above, by warning the negligence of the removal of the operating-part main unit 20 by the alarm sound, negligence of the removal of the operating-part main unit 20 can be easily recognized. However, since the operation of the apparatus is set so that ringing of the alarm sound is repeated each time the ignition key 30 is turned off, there can be a case where the user feels the alarm sound rasping.
Such a drawback would become more notable as the frequency of conditions where the ignition key 30 is turned off after the vehicle has stopped.
FIG. 4 shows another example of car-stereo equipments of the detachable type. In this example, a protecting circuit 36 is provided in the apparatus main unit 10. The protecting circuit 36 is connected between the 5 V power supply terminal 12a and the 8 V power supply terminal 12c and between the 5 V power supply circuit 17 and the 8 V power supply circuit 18.
When a short-circuit occurs between the 5 V power supply terminal 12a and another terminal or between the 8 V power supply terminal 12c and another terminal or the like, the microcomputer 19 detects such a short-circuit and immediately makes the protecting circuit 36 operative, thereby shutting off the power supplies from the 5 V power supply circuit 17 and 8 V power supply circuit 18.
By this operation, even in cases where any one of the terminals on the apparatus main unit 10 which is exposed is erroneously short-circuited or static electricity is applied to any one of the terminals, the protecting circuit 36 immediately operates, so that a breakage of the internal circuit of the apparatus main unit 10 is prevented.
In the conventional car stereo equipment mentioned above, after the operating-part main unit 20 has been removed from the apparatus main unit 10, the shutter 13 is slid in the closing direction and the terminals in the connector 12 are covered, thereby preventing an electric shock, a short-circuit, or the like.
In another car stereo equipment, a protecting circuit 36 is provided on the apparatus main unit 10 and when the microcomputer 19 detects the short-circuit occurring between any terminals, the protecting circuit 36 is immediately made operative and the power supplies from the 5 V power supply circuit 17 and 8 V power supply circuit 18 are shut off, thereby preventing damages to the internal circuit of the apparatus main unit 10.
According to the former car stereo equipment, however, in order to prevent an electric shock, a short-circuit, or the like, the shutter 13 is slidably provided. In designing car stereo equipments whose dimensions or the like are generally limited, accordingly, it is extremely difficult to determine the position of the shutter 13, the position of a sliding mechanism to slide the shutter 13, and the like. Since it is necessary to allow the sliding motion of the shutter 13, parts for the slide of the shutter and the like are also needed. This also leads to a drawback that the increase in number of parts causes increase in the cost of the car stereo equipment. Further, the shutter 13 often has a structure such that it is manually opened or closed for the purpose of cost reduction. Not only the opening/closing operation of the shutter 13 is troublesome but also the user may frequently forget to close the shutter 13, so that the inherent purpose for prevention of the short-circuit or the like cannot be often accomplished.
According to the latter car stereo, on the other hand, in spite of the fact that the breakage of the internal circuit of the apparatus main unit 10 is prevented by the protecting circuit 36 provided in the apparatus main unit 10, the apparatus is constructed by paying an attention to the prevention of the breakage of the internal circuit, so that a structure to prevent the short-circuit of the terminals is not improved yet. Since the apparatus has the protecting circuit 36, drawbacks such that not only the circuit construction of the apparatus main unit 10 is complicated but also the costs of the car stereo rise in a manner similar to that mentioned above still remain.